Fix nightly warnings 2024 june

[conradludgate]

Problem

new clippy warnings on nightly.

Summary of changes

broken up each commit by warning type.

1. Remove some unnecessary refs.
2. In edition 2024, inference will default to ! and not ().
3. Clippy complains about doc comment indentation
4. Fix Trait + ?Sized where Trait: Sized.
5. diesel_derives triggering non_local_defintions

Checklist before requesting a review

• I have performed a self-review of my code.
• If it is a core feature, I have added thorough tests.
• Do we need to implement analytics? if so did you add the relevant metrics to the dashboard?
• If this PR requires public announcement, mark it with /release-notes label and add several sentences in this section.

Checklist before merging

• Do not forget to reformat commit message to not include the above checklist

[github-actions]

3036 tests run: 2921 passed, 0 failed, 115 skipped (full report)

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Flaky tests (2)

Postgres 16

• test_statvfs_pressure_usage: release
• test_subscriber_restart: release

Code coverage* (full report)

• functions: 32.7% (6968 of 21285 functions)
• lines: 50.1% (54785 of 109302 lines)

* collected from Rust tests only

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_{The comment gets automatically updated with the latest test results
80b7b9b at 2024-07-11T14:39:36.033Z :recycle:}